Towards soil water scarcity? An exploratory time-series analysis of the aridity index in Castelporziano forest, Rome

A month time series of the Aridity Index (AI) was analyzed over 32 years (1981–2012) in Castelporziano (Rome, central Italy) with the objective to identify changes in climate seasonality and trend components. The AI decreased in the last 16 years (1997–2012) compared with the previous time interval (1981–1996). The largest decline was observed in spring and summer, especially in April and June. Time series analysis indicates a trend towards aridity with both seasonal and annual components and a moderate 6-years cycle component. Irregularities in time series indicate three distinct dry periods with a persistently high aridity index (1988–1989, 2003 and 2006–2007). These time intervals represent exceptional drought episodes in central Italy and confirm the general trend observed at the national level. The implications of the increased aridity in Castelporziano forest are finally discussed in the light of preservation of a typical agro-forest landscape in the Tyrrhenian coast around Rome.